The present invention relates to a system for generating high-hydrogen gas as well as to a process for starting the device.
Japanese Patent Document JP 4-325401 A discloses a system of the above-mentioned type for generating hydrogen, which has a pre-reforming stage and a shift stage that are separated from one another by a heat exchange surface. At least a portion of the thermal energy required for the water vapor reforming is transferred from the preliminary gas purification stage to the pre-reforming stage.
It is an object of the present invention to provide a system for generating high-hydrogen gas which has a simpler and more compact construction, a higher heat transfer and an improved gas purification function. In addition, it is an object of the present invention to provide a process for the simple and fast starting of the device.
This and other objects and advantages are achieved by the present invention by adding air in a metered manner, and by the subsequent selective catalytic oxidation of the carbon monoxide, thereby ensuring a higher heat development in the gas purification stage and thus a better heating of the reaction space. In addition, a selective oxidation stage, in contrast to a shift stage, has an improved gas purification function. Furthermore, the system has a good cold starting capability, a good dynamic behavior during load changes and an improved efficiency, permitting use in mobile applications. The improved heat yield in the CO oxidation stage is sufficient for completely heating the reformer. An additional heating device is not required. Further, the two reactions can be coupled by a suitable design of the reaction rates in the two partial systems such that a defined temperature level is automatically set in the system. A high-expenditure temperature control is therefore not required.
During the starting of the system, the CO oxidator can temporarily be operated as a catalytic burner, so that the system can be brought to the required operating temperature in a simple and rapid manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.